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Authir · Sep 16, 2009, 08:53 AM

Hey There,

I'm a student studying to be an Electrician and I came across a question in my book I couldn't find a good enough answer for which is.

What is the meaning of Calculated Load?

Thanks!
~Authir

Perito · Sep 16, 2009, 09:04 AM

This could be either the amount of current that you calculate to be going through the load or possibly the effective resistance of the load, itself. Normally, this is calculated (on a simple resistive circuit) using Ohm's law.

KISS · Sep 16, 2009, 11:23 AM

Without seeing it in context, I can only take a guess.

A load can be calculated by knowing Watts and voltage, for instance. Usually your interested in amps.

A "calculated load" could also mean a the load that one should use if the load is considered "continuous". That load is multiplied by (1/0.8)

Best guess without context surrounding the term.

ohb0b · Sep 17, 2009, 11:17 PM

The calculated load is the load determined by the calculations in NEC Article 220.

It is arrived at by considering various demand factors.

For example, say you have a 2000 square foot residence, and a 2000 square feet of office space. In the office, you will probably have all the lights turned on during business ours, so the service must be designed to operate the entire lighting load.
In a residence, you do not generally turn on every light in the house (unless you have kids... sigh) so you are allowed to apply a "demand factor" to approximate actual usage, and your service does not have to be as large.

Another typical demand factor is when you have heating and air conditioning equipment, the service does not have to be large enough to operate them at the same time.